Die casting is a manufacturing process for
producing metal parts by forcing molten metal under high pressure into a die
cavity. Generally speaking, these die or mold cavities are created with
hardened tool steel that have been previously machined to the net shape or near
net shape of the die cast parts. This process allows products to be made with
high degree of accuracy and repeatibility. The Die casting process also produce
fine details such as textured surfaces or names without requiring further
processing.
The ability of producing high detailed and
high accuracy parts make Die casting a suitable choice for mass produced
product. The moment you wake up you are surrounded products that are produced
by the Die casting process. When you turn the faucet, you open the door knob,
when you drive your car, almost every product or part of the product you use in
your daily life is produced using this process.
The Die casting process usually produce
parts using primarily non-ferrous metals, such as zinc, copper, aluminum and
magnesium. Over the years, many different alloys have been developed to meet
certain type of needs and requirements of each application.
Type of Die casting processes
The Die casting process can be further
divided into two different categories:
Hot Chamber Die casting
Cold Chamber Die casting
Hot Chamber Die casting is the process
where the injection system is immersed in pool of molten metal hence the
name. The furnace is attached to the
machine via a feeding system called a gooseneck. As the cycle begins the piston will retracts,
which allows the molten metal to fill the “gooseneck” from a port in the
injection cylinder. As the plunger move downwards, it seals the port and forces the molten metal
through the gooseneck and nozzle into the die.
Once the metal solidifies, the plunger will pull upwards. Afterwards, the die will open and the part is
ejected. The advantage this process its
short cycle time as it does not require metal to be transported from a separate
furnace. Unfortunately, this Die casting
process is only suitable for alloys that do not attack the injection cylinder
such as zinc, magnesium and copper.
Cold Chamber Die casting is the process of
using a ladle to transport the molten metal from the holding furnace into the
unheated shot chamber or injection cylinder.
This metal is then shot into the die by using a hydraulic piston. The main disadvantage of this process is that
it is relatively slower compared to the Hot Chamber Die casting process.
However, this process is primarily used for manufacturing aluminum parts
as molten aluminum alloys have a tendency to attack and erode the metal
cylinders, plungers and dies greatly shortening their tool life.
History
The Die casting process dates back to the
mid 1800s, when a patent was awarded to Sturges in 1849 for the first manually
operated machine for casting printing type.
However, it was not until 20 years later that this process has been used
to produce other consumer products such as phonographs and cash registers.
In the beginnings, tin and lead are the
primary alloys used for the Die casting process, but these alloys have been
replaced by zinc and aluminum since the 1920s.
As technology advances, the Die casting
process has become more and more efficient.
New technologies allow greater pressure in the injection process, thus
allowing us to produce parts that are closer to net shape and higher integrity
than ever before.
Advantages of Die casting Parts
One of the main advantages of Die casting
is the ability to produce parts and products with a wide range of shape and
sizes. Unlike other manufacturing
processes such as extrusion, the Die casting process does not limit the shape
of parts and in most cases will be the net shape of the parts.
Durability:
Unlike plastic parts, die cast parts are
stronger than their plastic counterparts.
In most cases, this allows parts to be produced with thinner walls while
maintaining the strength that is required for its application. Furthermore, die cast parts are able to
withstand to a broader range of temperature, making it more ideal in harsh
temperatures and working environments.
Mass production at high speed:
Since the Die casting process can allow
manufacturers to produce complex parts to net shape, there is little or no
machining processes required thus reducing the production time making Die
casting one of the most effective process to mass produce non-ferrous metal complex
parts.
Green Manufacturing:
How long does it takes for plastic to
biodegrade? According to scientists,
plastics takes at least a few hundreds of years to degrade fully. This means that obsolete plastic products are
pilled up in the landfills, polluting our beaches, killing millions of sea
animals and causing health hazards to the inhabitants in our
neighborhoods. Unlike plastic, Die
casting parts are primarily made of recycled material. On average, approximately 95% of the metal is
recycled from salvaged parts making it a sustainable material that can be used
over and over again without degradation.
Thinner Wall Castings:
Compared with sand and permanent mold
castings, the Die casting process is able to produce parts with thinner walls
due to the high pressure during the injection process. This allows lightweight construction as well
as eliminate or reduce the need of secondary operations.
Casting with inserts:
The Die casting process allows inserts to
be cast-in to form certain features such as threaded inserts, heating elements
or high strength bearing surfaces.
